System, method, and computer-readable medium for provisioning dual-homed voice call continuity

ABSTRACT

A system, method and computer-readable medium for concurrent support of Voice Call Continuity (VCC) capabilities in both the enterprise space and the carrier space are provided. The enterprise VCC functionality is used when the user is located in the enterprise domain which does not impact the carrier&#39;s network while the carrier VCC capability is used when the user is located in the carrier domain to support seamless handover between the wireless networks that the carrier may offer. The carrier VCC anchoring point and the enterprise VCC anchoring point may communicate with each other to confirm and inform the other anchoring point that a call handover is occurring or will occur.

RELATED APPLICATION DATA

This patent application is a continuation of U.S. patent applicationSer. No. 12/196,097, entitled “SYSTEM, METHOD AND COMPUTER-READABLEMEDIUM FOR PROVISIONING DUAL-HOMED VOICE CALL CONTINUITY” filed Aug. 21,2008, issued U.S. Pat. No. 8,705,487, issued Apr. 22, 2014, which claimsthe benefit of provisional U.S. Patent Application Ser. No. 60/957,121,entitled “Dual-Homed Voice Call Continuity”, filed Aug. 21, 2007, eachof which is hereby incorporated by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to commonly assigned U.S. ProvisionalApplication No. 60/957,121, entitled “Dual-Homed Voice Call Continuity,”filed on Aug. 21, 2007, the entirety of which is hereby incorporated byreference herein.

FIELD OF THE INVENTION

The present disclosure relates to telecommunications and, moreparticularly, to provisioning voice call continuity in atelecommunications network.

BACKGROUND

Corporations are increasingly relying on the use of cellular technologyby their employees, yet enterprises have traditionally lacked adequatemeans to control cellular service in terms of costs, Quality of Service,and corporate monitoring. This is because cellular service hasconventionally been controlled by wireless carrier networks and managedindependently of, and with no connectivity to, the enterprise voice anddata networks.

Many contemporary mobile phones are available that support both cellularand other broadband radio technologies. For example, numerous mobilephones, or user equipments, are currently or will be commerciallyavailable that support a combination of the Global System for Mobilecommunications (GSM) and/or CDMA IS-95, as well as 3G technologies suchas UMTS, HSPA or CDMA 1×RTT, 4G technologies such as LTE or WiMAX, andunlicensed technologies such as Wi-Fi. A wide range of Internetapplications may then be accessed from user equipments featuringdual-mode, tri-mode or multi-mode technologies using wireless broadband,such as 3G UMTS, 4G WiMAX and unlicensed WiFi. For example, voice overIP (VoIP) traffic may be carried over alternative radio interfaces, suchas 3G UMTS, 4G WiMAX and unlicensed WiFi.

The 3GPP has defined the Voice Call Continuity (VCC) specifications inorder to describe how a voice call may be maintained as a mobile phonemoves between circuit switched and packet switched radio domains. Asreferred to herein, a 2G service comprise a circuit switched service,and a 3G, 4G or unlicensed service comprises a packet switched service.

When a user equipment (UE) becomes attached and detached from wirelessaccess points, such as WiFi hotspots, a client application in acontemporary UE communicates the radio conditions to a VCC platform inthe network. This allows circuit switched and IP call legs to beoriginated and terminated such that the speech path is transferredbetween domains transparently to the end user.

Because most packet-switched access points utilize fixed backhaultechnologies, seamlessly moving between packet and circuit domainsallows the best quality and most cost efficient radio to be used at anygiven point in time, regardless of the transport technology used for themedia. Service providers are interested in VCC in order to offerproducts directed to particular market segments, e.g., enterprise users.Enterprises are also interested in VCC typically for enabling dual-modedevices, e.g. GSM and WiFi, to be able to circumvent the serviceproviders network.

SUMMARY OF THE INVENTION

Embodiments disclosed herein provide mechanisms for supporting VoiceCall Continuity (VCC) capabilities in both the enterprise space and thecarrier space simultaneously. The enterprise VCC functionality is usedwhen the user is located in the enterprise domain which does not impactthe carrier's network while the carrier VCC capability is used when theuser is located in the carrier domain to support seamless handoverbetween the wireless networks that the carrier may offer. The carrierVCC anchoring point and the enterprise VCC anchoring point maycommunicate with each other to confirm and inform the other anchoringpoint that a call handover is occurring or will occur.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures, in which:

FIG. 1 is a diagrammatic representation of a network architecture inwhich embodiments disclosed herein may be implemented;

FIG. 2 is a simplified block diagram of an exemplary mobile terminal inwhich embodiments may be implemented;

FIG. 3 is a diagrammatic representation of an exemplary softwareconfiguration of a mobile terminal implemented in accordance with anembodiment;

FIGS. 4A-4D depict exemplary signaling flows for a multi-mode mobilehandover featuring voice call continuity from a circuit to a packetnetwork whereby seamless handover mechanisms are provided for callsestablished on the cellular side of the network by carrier VCCcapabilities in accordance with an embodiment;

FIGS. 5A-5C depict exemplary signaling flows for a multi-mode mobilehandover featuring voice call continuity from a circuit network to apacket network whereby seamless handover mechanisms are provided forcalls established on the cellular side of the network by enterprise VCCcapabilities implemented in accordance with another embodiment;

FIGS. 6A-6D depict exemplary signaling flows for a multi-mode mobilehandover featuring voice call continuity from a packet network to acircuit network whereby seamless handover mechanisms are provided forcalls established on the cellular side of the network by carrier VCCcapabilities in accordance with an embodiment;

FIGS. 7A-7D depict exemplary signaling flows for a multi-mode mobilehandover featuring voice call continuity from a packet network to acircuit network whereby seamless handover mechanisms are provided forcalls established on the enterprise side of the network by enterpriseVCC capabilities in accordance with another embodiment;

FIG. 8 is a flowchart that depicts processing of an enterprise voicecall continuity routine that facilitates handover collaboration betweena carrier network and an enterprise network in accordance with anembodiment; and

FIG. 9 is a flowchart that depicts processing of a carrier voice callcontinuity routine that facilitates handover collaboration between acarrier network and an enterprise network in accordance with anembodiment.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Heretofore, no mechanisms have been provided for enabling support forVCC capabilities in both the enterprise space and the carrier (serviceprovider) space simultaneously and advantageously for both theenterprise and the carrier.

FIG. 1 is a diagrammatic representation of an exemplary network system100 in which embodiments disclosed herein may be implemented. A carriernetwork 150 includes a gateway Mobile Switching Center (GMSC) 151 thatprovides an interface between the public switched telephone network(PSTN) 130 and carrier network 150. GMSC 151 determines which MSCcurrently services a called mobile terminal. Carrier network 150includes a switching sub-system (SS) 152 and a base station sub-system(BSS) 156. Each of SS 152 and BSS 156 contain a number of functionalunits well understood by those skilled in the art, and a detailedexplanation of the various components is unnecessary. Nevertheless, acursory review of various components is provided. SS 152 may contain aMSC 153, a Home Location Register (HLR) 154, and a Visitor LocationRegister (VLR) 155. MSCs carry out switching functions and manage thecommunications between mobile phones and the PSTN 130. HLR 154 comprisesthe central database that contains details of each mobile phonesubscriber that is authorized to use the cellular core network. VLR 155comprises a database which stores information about all the mobileterminals that are currently serviced by the associated MSC. VLR 155stores various information regarding the mobile terminals, such as thecurrent location area identity that specifies a particular base stationcontroller (BSC) currently servicing the mobile terminal.

Various other sub-systems or functional modules may, and typically are,included in SS 152, such as an Authentication Center, an EquipmentIdentity Register, or various other functions. A serving general packetradio service (GPRS) support node (SGSN) 160 may be included in thecarrier network 150 to facilitate provisioning of packet services to andfrom mobile terminals in network 150. To this end, the SGSN mayinterface with a BSC 157 for providing a packet interface therewith.GPRS provides mobility management, session management and transport forInternet Protocol packet services in cellular packet networks.

BSS 156 contains a BSC 157 that may be in communication with and incontrol of a plurality of Base Transceiver Stations (BTSs) 158 a-158 c.Each individual BTS 158 a-158 c under the control of a given BSC 157 maydefine a radio cell operating on a set of radio channels therebyproviding service to a UE 125.

As is understood, various GPRS infrastructure may be included in network150 to provide packet services to mobile terminals. In general, the SGSN160 may interface with a wireless media gateway (WMG) 159 that iscommunicatively coupled with the MSC 153. The WMG 159 typically includesa control function and a media function. The WMG 159 may include asignaling interface, e.g., the Session Initiation Protocol (SIP), with aserving-call session control function (S-CSCF) 162. The WMG 159 mayinclude a circuit switched, e.g., a time division multiplexed (TDM),interface with the MSC and provides media conversion of circuit-switcheddata and packet-switched data. The WMG 159 may include a packet-switchedinterface with the SGSN 160. A gateway GPRS support node (GGSN) 161 mayinterface the GPRS backbone with an external packet network, such as theInternet 140. Thus, circuit-switched data, such as TDM voice calls, maybe provided to a UE 125 over an air-interface via the MSC and BSCinterface. Packet-switched data may be provided to a UE 125 via the WMG159, SGSN 160, and BSC 157 interface.

SGSN 160 may interface with various subsystems of network 150. Forexample, SGSN 160 may have a Gs interface with MSC 153 and VLR 155 thatfacilitates paging and station availability notification when performingdata transfers. SGSN 160 may additionally have a Gr interface with HLR154 through which messaging may be performed, for example, over theMobile Application Part protocol.

The S-CSCF 162 provides a central signaling plane node that mayadditionally provide session control. The S-CSCF 162 may be implementedas a SIP server. The S-CSCF may manage SIP registrations, selectapplication servers for a particular session, provide routing services,enforce carrier policies, as well as provisioning of various otherservices. The S-CSCF 162 may host or interface with a carrier VCCservice 163 that provides voice call continuity services when the VCC isanchored in the carrier network. The S-CSCF 162 may interface with thecontrol function of the WMG 159.

Carrier network 150 may additionally include, or alternatively interfacewith, a WiFi network 180 that may provide packet switched services to asuitable UE. In one implementation, WiFi network 180 may include variousaccess points, or hot spots, and a suitably adapted UE may roam ortransition from the carrier network to the WiFi network. In the eventthe UE is attached to the carrier network in a circuit-switched mode, ahandover of the UE from the circuit-switched carrier infrastructure tothe packet-switched WiFi network 180 may be performed utilizing VCCservices. In another event where the UE is attached to the carriernetwork in a packet-switched mode, a handover of the UE from thepacket-switched carrier infrastructure to the packet-switched WiFinetwork 180 may be performed utilizing packet-to-packet handoverservices.

System 100 may include an enterprise network 170 that includes a PBX 171that provides service to any number of extensions, e.g., enterpriseterminal devices 172 a-172 n. Additionally, PSTN 130 may interface withenterprise network 170, e.g., by a tandem or other switch coupled withenterprise router 174. Enterprise network 170 may include an enterprisegateway server (GS-E) 176 that may be communicatively coupled with acarrier gateway server (GS-C) 192 deployed in, or interconnected with,carrier network 150. Enterprise network 170 may include or interfacewith a WiFi network 190, or other packet switched network, with whichdual mode, or greater, UEs adapted for packet switched communicationsmay access.

A single enterprise network 170 is depicted to facilitate anunderstanding of the disclosed embodiments, but numerous enterprisenetworks may interface with GS-C 192. To this end, the GS-C 192 mayinclude, or interface with, an enterprise database 193 that facilitatesrouting of calls and associated signaling to an appropriate enterprisenetwork. For example, enterprise database 193 may maintain anassociation of directory numbers of terminal devices 172 a-172 n andMSISDNs of user equipment 126 a-126 n with an address or other referenceto the corresponding enterprise network, such as a uniform resourcelocator assigned to the GS-E 176.

GS-E 176 may interact with GS-C 192 deployed or interconnected withcarrier network 150. The connection between GS-E 176 and GS-C 192 may bemade over, for example, session initiation protocol (SIP) or otherprotocols. This configuration may enable carrier network 150 to have acentral point of control for interacting with multiple enterprises, andmay not require the use of SS7 messaging to the enterprise. Rather, itis possible to have a secure IP connection supporting SIP. This is alsouseful for offering a Centrex solution for interconnecting with acarrier-hosted PBX, or for interconnecting a carrier-hosted gatewayserver with enterprise-hosted PBX systems. GS-C 192 may support an SS7point code multiplexer in which only one or two point codes are neededto address all enterprises since GS-C 192 can identify for whichenterprise a message is intended. GS-E 176 may be adapted to provisionGS-C 192 automatically over an IP interface to manage subscribers, e.g.,to add new pilot directory numbers for new subscribers. Enterprisemembers may be allocated a respective Enterprise terminal device 172a-172 n as well as a mobile terminal, or user equipment, 126 a-126 n.

GS-E 176 may host or interface with an enterprise VCC service 177 thatprovides voice call continuity service when the VCC is anchored in theenterprise network in accordance with an embodiment. A UE that featuresdual-mode capabilities, or greater, that is adapted to operate in both acircuit switched mode and a packet switched mode may monitor the radioenvironment when the UE is operating in a particular network. In theevent that the UE detects another network that is desirable forhandover, the UE may attempt to register with the detected network. Forexample, the UE may be configured for preference of a wireless networkover another based on a threshold of the signal strength that itobserves from the network. When a UE requests a handover from a circuitswitched network to a packet switched network, or vice versa, a VCCservice may determine whether to allow or disallow the handover. Inaccordance with disclosed embodiments, the VCC handover decision may beconjunctively determined by both carrier and enterprise entities. In oneembodiment, carrier policies 194 may be evaluated by the GS-C todetermine whether to allow a requested handover. For example, carrierpolicies may specify maximum network loads over which requestedhandovers are to be denied, policies that disallow enterprise memberhandovers based on the time of day, enterprise member handoverdisallowance due to non-paid enterprise tariffs, or any variety of otherdecision criteria. In a similar manner, GS-E 176 may include orinterface with an enterprise policy database 178 that specifiesenterprise criteria for allowing or disallowing enterprise memberhandovers. For example, policy database 178 may specify times of the dayat which handovers are to be disallowed, maximum network capacities overwhich handovers to the network are to be disallowed, handover criteriabased on member UE location, or any variety of other policyspecifications. Further, the policies defined in enterprise policydatabase 178 may be specified on an enterprise-wide basis, an enterprisemember group basis, and/or an enterprise-member basis.

In another embodiment, a UE that features dual-mode capabilities, orgreater, that is adapted to operate in multiple disparate packetswitched modes, for example a carrier's 3G packet-switched network andan enterprise's WiFi packet-switched network or a carrier's 3Gpacket-switched network and a carrier's 4G packet-switched network, maymonitor the radio environment when the UE is operating in a particularnetwork. In the event that the UE detects another network that isdesirable for handover, the UE may attempt to register with the detectednetwork. For example, the UE may be configured for preference of awireless network over another based on a threshold of the signalstrength that it observes from the network. When a UE requests ahandover from one packet-switched network to another packet switchednetwork, a packet-to-packet handover service may determine whether toallow or disallow the handover. In accordance with disclosedembodiments, the packet-to-packet handover decision may be conjunctivelydetermined by both carrier and enterprise entities. In one embodiment,carrier policies 194 may be evaluated by the GS-C to determine whetherto allow a requested handover. For example, carrier policies may specifymaximum network loads over which requested handovers are to be denied,policies that disallow enterprise member handovers based on the time ofday, enterprise member handover disallowance due to non-paid enterprisetariffs, or any variety of other decision criteria. In a similar manner,GS-E 176 may include or interface with an enterprise policy database 178that specifies enterprise criteria for allowing or disallowingenterprise member handovers. For example, policy database 178 mayspecify times of the day at which handovers are to be disallowed,maximum network capacities over which handovers to the network are to bedisallowed, handover criteria based on member UE location, or anyvariety of other policy specifications. Further, the policies defined inenterprise policy database 178 may be specified on an enterprise-widebasis, an enterprise member group basis, and/or an enterprise-memberbasis.

In one embodiment, VCC handover decisions may be conjunctively madebetween the carrier network and the enterprise network. For example, fora VCC handover to be allowed, both the GS-C and the GS-E may be requiredto approve the handover. For example, the GS-C may disallow a VCChandover request approved by the GS-E. Likewise, the GS-E may disallow aVCC handover that is approved by the GS-C.

In another embodiment, VCC handover decisions may be conjunctively madebetween the carrier network and the enterprise network, however onenetwork may have authority to override the decision of the othernetwork. For example, for a VCC handover to be allowed, it is possiblethat the GS-C overrides a decision to disallow the handover request bythe GS-E. Likewise, it is possible that the GS-E overrides a decision todisallow the handover request that is disallowed by the GS-C.

From an IT organization perspective, GS-E 176 appears as an extension toPBX 171. To carrier network 150, GS-E 176 appears as a standardin-network endpoint for delivering calls. To PBX 171, GS-E 176 appearsas a set of standard PBX endpoints (e.g., deskphones, or IP clients).GS-E 176 mediates between the two disparate sets of network protocolsand state machines.

GS-C 192 may include the network functions for both voice (gateway MSC)and data (gateway GPRS Support Node or Home Agent), VoIP capability forinterconnecting carrier network 150 with Enterprise network 170 therebyeliminating PSTN interconnect charges, a billing gateway, and anext-generation Network Services gateway that enables third party valueadded services for the enterprise, such as mobile phoneactivation/de-activation, corporate directory integration based on IMS(IP Multimedia Subsystem), or other services. GS-C 192 may also includethe element management subsystem (EMS) and a service managementsubsystem for the operational support system (OSS).

PBX 171 and GS-E 176 may include or interface with an enterprise memberdatabase 179 that stores records or profiles that define services formembers of enterprise network 170. GS-E 176 may interface with memberdatabase 179 via a provisioning interface specific to PBX 171.Enterprise member database 179 may include records that specifyenterprise members and DID numbers of telephony devices allocatedthereto. Additionally, enterprise member database 179 may specify usagepolicies for enterprise members that may define, for example, allowablemobile terminal usage such as roaming capabilities, various preferredcall progressions to be provided to Enterprise members under variouscircumstances, and the like.

FIG. 2 is a simplified block diagram of an exemplary UE 125 in whichembodiments may be implemented. UE 125 includes an antenna 202 that maybe coupled with an RF switch 204, e.g., a duplexer, coupled with an RFtransceiver 206. Transceiver 206 may be coupled with an analog baseband208 that may handle a variety of analog signal processing functions. Inthe present example, analog baseband 208 is interconnected with amicrophone 210, a keypad 212, a vibrator 214 or other ring alertmechanism, a headset speaker 216, and a loudspeaker 230 for output ofspeakerphone and incoming call alert audio. Analog baseband 208 mayinclude or interface with an analog to digital converter for convertinganalog input supplied to microphone 210 into a digital format that maybe supplied to a digital baseband 218. Digital baseband 218 mayinterface with various digital components of UE 125, such as a memory220, an optional subscriber identity module (SIM) card 222, and a liquidcrystal display controller 226 that drives a display 228. Memory 220 maybe implemented as a flash memory, a random access memory, anelectronically erasable programmable read-only memory, another solidstate device, or a combination thereof. Digital baseband 218 mayadditionally include or interface with one or more encoders, digital toanalog converters, or other modules. A power supply 232 may be coupledwith various system modules as is understood. The implementation of UE125 depicted in FIG. 2 is exemplary only, and UE 125 may be implementedas any suitable device adapted to interface with a carrier network. UE125, also referred to as a mobile terminal, may be implemented as apersonal digital assistant (PDA), a mobile phone, a computer, or anotherdevice adapted to interface with a carrier network.

FIG. 3 is a diagrammatic representation of an exemplary softwareconfiguration 300 of a UE implemented in accordance with an embodiment.In the exemplary configuration of FIG. 3, the UE is configured withaccess network-specific software entities 360 a-360 b, e.g., protocoland driver software associated with a particular access networktechnology, such as GSM, UMTS, CDMA or another suitable radio accessnetwork, and is dependent on the particular network in which the UE isto be deployed. While configuration 300 depicts a UE adapted fordeployment in two access network technology types, the UE may beimplemented as a multi-mode device adapted for deployment in two or moreaccess technology networks. Particularly, software configuration 300includes at least one software entity, such as entity 360 a, thatfacilitates access to a circuit switched network, and another softwareentity, such as entity 360 b, that facilitates access to a packetswitched network. The particular configuration 300 is illustrative onlyand is provided only to facilitate an understanding of embodimentsdisclosed herein.

In the illustrative example, configuration 300 includes a modem driver302 a-302 b for providing a respective physical interface with an accessnetwork in which the UE may be deployed. Access-stratum 304 a-304 b andnon-access stratum 306 a-306 b may be included in configuration 300.Radio interface 308 a-308 b may be communicatively coupled with lowerlayers of configuration 300 and may additionally interface with networkand session management layers, e.g., a network stack 310 such as aTCP/IP layer.

In accordance with disclosed embodiment, the ability to support VCCcapabilities in both the enterprise space and the carrier spacesimultaneously is provided.

Both the enterprise VCC and the carrier VCC functionality are invokedwhen the user of a multi-mode device requires support for a seamlesshandover between the wireless networks that the carrier may offer, suchas 2G GSM and CDMA circuit voice and packet networks including 3G UMTS,HSPA, 1×RTT voice over packet, 4G LTE, WiMAX voice over packet, orunlicensed WiFi voice over packet. Similarly, the seamless handoverwhereby both the enterprise and carrier VCC functionality are invokedcan also be supported between the carrier's 2G circuit voice and anenterprise's unlicensed WiFi voice over packet network, and between thecarrier's 3G or 4G packet networks and an enterprise's unlicensed WiFivoice over packet network.

FIGS. 4A-4D depict exemplary signaling flows for a multi-mode mobilehandover featuring voice call continuity from a circuit to a packetnetwork implemented in accordance with an embodiment whereby seamlesshandover mechanisms are provided for calls established on the cellularside of the network by carrier VCC capabilities.

In this implementation, the carrier GS-C acts as the primary contactpoint by the multi-mode device when a handover is to occur, and as suchthe GS-C performs the VCC handover with permission obtained from theGS-E. In the particular example, a call is handed off between 2G circuitvoice and either 3G, 4G or WiFi packetized voice networks whileremaining anchored in the enterprise such that enterprise services,e.g., PBX features, call monitoring, and the like, may be provided tothe call and maintained over the seamless handover.

In the signaling flow 400 a of FIG. 4A, the user of a multi-mode deviceoriginates a call over the 2G network to a desk phone in the enterprise.From the 2G MSC after conversion of the call into an IMS call viatriggering or another suitable method, a call invite is issued to theS-CSCF (step 402). The S-CSCF, based on initial filter criteria, sendsthe invite to the GS-C that features the carrier based VCC functions(step 404). The GS-C recognizes the appropriate enterprise based on theuser profile and number, and then requests the GS-E for the policy to beapplied to the call (step 406). The GS-E returns a redirection response,e.g., a SIP 302 response, with a pilot number to which the call is to berouted (step 408). The GS-C returns the invite with the pilot number tothe S-CSCF (step 410), and the S-CSCF routes the call to the pilotnumber which is supported by the enterprise PBX (step 412). The PBX, onreceipt of the inbound call, sends the invite to the GS-E (step 414)which replaces the pilot number with the original dialed digits usingthe number that it has previously stored in association with the pilotnumber. The GS-E then routes the call to the PBX for delivery to thedesk terminal (step 416). The desk terminal may comprise, for example, afixed landline telephone device, a software client operating on acomputing platform, or a mobile terminal communicatively interfaced withthe PBX. The PBX then routes the call to the desk terminal (step 418).The desk terminal then returns an invite acknowledgement (step 420),e.g., a SIP 200 response.

The PBX forwards the acknowledgment to the GS-E (step 422), whichreplies with an acknowledgment (step 424). The PBX then forwards theacknowledgment to the S-CSCF (step 426) which forwards theacknowledgment to the UE via the 2G MSC (step 428), and the media pathis set up (step 430). In this instance, the call comprises a 2G, orcircuit switched call leg, between the 2G MSC and a carrier WMGinterconnected with the 2G MSC, and packet switched call legs betweenthe WMG and the PBX, the PBX and the enterprise gateway server, and theenterprise gateway server and the desk terminal.

In the signaling flow 400 b depicted in FIG. 4B, assume the UE now movesinto a coverage area which includes 3G, 4G or unlicensed WiFi packetizedservice. In the present example, assume the UE identifies 3G servicesare provided by the carrier's UMTS or CDMA 1×EV-DO Rev. A packetnetwork. Accordingly, the UE now attempts to initiate a handover requestto the carrier's VCC service by sending an invite to the CSCF (step 432)over the carrier's 3G network. The request by the UE may be sent to anIP address or to a domain name that is resolved to the carrier's VCCservice via the carrier's S-CSCF. The S-CSCF, based on initial filtercriteria, sends the invite to the GS-C for handling (step 434). The GS-Cmay then evaluate various carrier policies specified in carrier policydatabase 194 for determining whether to allow or disallow the handover.If the GS-C allows the handover to occur based on criteria analyzed inthe GS-C (for example, the carrier determines there is sufficientcapacity on the 3G packetized network to handle this call), then theGS-C forwards the request to the GS-E (step 436) hosting the enterpriseVCC function. If the GS-E allows the handover to occur based on criteriaanalyzed in the GS-E (for example, the enterprise elects to allow forreduced tariffs or other enterprise policy criteria evaluated inenterprise policy database 178) then the GS-E informs the GS-C toproceed (step 438). The GS-C then sends a re-invite for the leg of thecall to the desk phone to the S-CSCF (step 440). The S-CSCF thenforwards the re-invite to the enterprise PBX (step 442), which forwardsthe re-invite to the GS-E (step 444) which responds to the PBX (Step446). The PBX forwards the re-invite to the desk terminal (step 448),and the desk terminal acknowledges the invite (step 450). The PBX thenforwards the acknowledgment to the GS-E (step 452) and the GS-E providesan acknowledgment thereto (step 454). The PBX forwards theacknowledgment to the S-CSCF (step 456) which provides theacknowledgment to the GS-C (step 458) that, in turn, replies with anacknowledgment (step 460). The S-CSCF then provides an acknowledgementto the 3G MSC (step 462). The GS-C provides a BYE message to the S-CSCFfor terminating the circuit switched call leg (step 464). The S-CSCFthen forwards the BYE message to the 2G MSC (step 466) which may providean acknowledgment thereto (step 468). The S-CSCF then forwards anacknowledgment to the GS-C (step 470) and the media path is set upthereby completing the call handover (step 472). The call then comprisespacket-switched call legs between the 3G MSC and the PBX, the PBX andthe enterprise gateway server, and the enterprise gateway server and thedesk terminal.

Returning to the case where the UE attempts to initiate a handoverrequest to the carrier's VCC service by sending an invite to the S-CSCF(step 432), and the S-CSCF sends the invite to the GS-C for handling(step 434) as depicted by the signaling flow 400 c of FIG. 4C. If theGS-C instead disallows the handover to occur based on criteria analyzedin the GS-C (for example, the carrier determines there is insufficientcapacity on the 3G packetized network to handle this call or othercriteria specified in the carrier policy database 194), then the GS-Cresponds with a Bye message to the S-CSCF (step 482) indicating thehandover request has been denied, which is then sent via the 3G MSC(step 484) to the UE. The handover request is terminated and the UEremains connected to the 2G MSC.

If the GS-C allows the handover to occur upon receipt of the invitebased on evaluated carrier policies, the GS-C then sends the request tothe GS-E for handling (step 436) as depicted by the signaling flow 400 dof FIG. 4D. If instead the GS-E disallows the handover to occur based oncriteria analyzed in the GS-E (for example, the enterprise elects tomaintain the call on the 2G network to avoid potential high cost datatariffs, to maintain voice quality or for other enterprise policycriteria specified in enterprise policy database 178), then the GS-Eresponds with a Bye message to the GS-C indicating the handover requesthas been denied (step 480), which is sent to the S-CSCF (step 482)indicating the handover request has been denied. The Bye message is thensent to the UE via the 3G MSC (step 484). The handover request isterminated and the UE remains connected to the 2G MSC.

FIGS. 5A-5C depict exemplary signaling flows for a multi-mode mobilehandover featuring voice call continuity from a circuit network to apacket network implemented in accordance with another embodiment wherebyseamless handover mechanisms are provided for calls established on thecellular side of the network by enterprise VCC capabilities. In thisimplementation, the enterprise GS-E acts as the primary contact point bythe multi-mode device when a handover is to occur, and as such the GS-Eperforms the VCC handover with permission obtained from the GS-C. In theparticular example, a call is handed off between 2G voice network and a3G/4G/WiFi packet network while remaining anchored in the enterprisesuch that enterprise services, e.g., PBX features, call monitoring, andthe like, may be provided to the call and maintained over the seamlesshandover.

In the signaling flow 500 a depicted in FIG. 5A, assume the user of amulti-mode device is already in a 2G circuit call as previouslydescribed in FIG. 4A. Following therefrom in FIG. 5A, assume the UE nowmoves into a coverage area which includes 3G, 4G or unlicensed WiFipacketized service. In the present example, assume the UE identifies 3Gservices are provided by the carrier's UMTS or CDMA 1×EV-DO Rev. Apacket network. Accordingly, the UE now attempts to initiate a handoverrequest to the enterprise's VCC service by sending an invite to the GS-Ehosting the enterprise VCC function (step 502). The request by the UEover the carrier's 3G network may be sent to an IP address or to adomain name that is resolved to the enterprise's VCC service. If theGS-E allows the handover to occur based on criteria analyzed in the GS-E(for example, the enterprise elects to allow for reduced tariffs), thenthe GS-E forwards the request to the GS-C (step 504) hosting the carrierVCC function. If the GS-C allows the handover to occur based on criteriaanalyzed in the GS-C (for example, the carrier identifies that theenterprise has subscribed to this service, the carrier identifies thereis insufficient packet coverage to maintain the packetized voice call on3G, or for other carrier policy criteria) then the GS-C informs the GS-Eto proceed (Step 506). The GS-E then sends a re-invite for the leg ofthe call to the desk phone to the PBX (step 508) which responds to theGS-E (Step 510). The GS-E then provides an acknowledgement to the UE viathe 3G MSC (step 512). The GS-E informs the 2G MSC via a carrier WMGinterconnected with the 2G MSC to terminate the circuit switched callleg (step 514) to which the 2G MSC responds (step 516), and the mediapath is set up thereby completing the call handover (step 518). The callthen comprises packet-switched call legs between the 3G MSC and the PBX,the PBX and the enterprise gateway server, and the enterprise gatewayserver and the desk terminal.

Returning to the case where the UE attempts to initiate a handoverrequest to the enterprise's VCC service by sending an invite to the GS-E(step 502), and the S-CSCF sends the invite to the GS-C for handling(step 504), if the GS-C instead disallows the handover to occur based oncriteria analyzed in the GS-C (for example, the carrier determines thereis insufficient capacity on the 3G network to maintain this call, theenterprise has not subscribed to this service or for other carrierpolicy criteria), then the GS-C responds with a Bye message to the GS-E(step 522) indicating the handover request has been denied as depictedby the signaling flow 500 b of FIG. 5B. The Bye message is then sent tothe UE via the 3G MSC (step 524). The handover request is terminated andthe UE remains connected to the 2G MSC.

If instead the GS-E disallows the handover to occur based on criteriaanalyzed in the GS-E (for example, the enterprise elects to maintain thecall on the 2G network to avoid potential high cost data tariffs, tomaintain voice quality or for other enterprise policy criteria), thenthe GS-E responds with a Bye message transmitted to the UE via the 3GMSC (step 520) as depicted by the signaling flow 500 c of FIG. 5C. Thehandover request is terminated and the UE remains connected to the 2GMSC.

FIGS. 6A-6D depict exemplary signaling flows for a multi-mode mobilehandover featuring voice call continuity from a packet network to acircuit network implemented in accordance with an embodiment wherebyseamless handover mechanisms are provided for calls established on thecellular side of the network by carrier VCC capabilities.

In this implementation, the carrier GS-C acts as the primary contactpoint by the multi-mode device when a handover is to occur, and as suchthe GS-C performs the VCC handover with permission obtained from theGS-E. In the particular example, a packetized voice call over a 3Gpacket network is handed off to a 2G voice network while remaininganchored in the enterprise such that enterprise services, e.g., PBXfeatures, call monitoring, and the like, may be provided to the call andmaintained over the seamless handover.

In the signaling flow 600 a depicted in FIG. 6A, the user of amulti-mode device originates a packetized voice call over the 3G networkto a desk phone in the enterprise. A call invite is issued by the UEover the 3G packet network to the S-CSCF (step 602). The S-CSCF, basedon initial filter criteria, sends the invite to the GS-C that featuresthe carrier based VCC functions (step 604). The GS-C recognizes theappropriate enterprise based on the user profile and number, and thenrequests the GS-E for the policy to be applied to the call (step 606).The GS-E returns a redirection response, e.g., a SIP 302 response, witha pilot number to which the call is to be routed (step 608). The GS-Creturns the invite with the pilot number to the S-CSCF (step 610), andthe S-CSCF routes the call to the pilot number which is supported by theenterprise PBX (step 612). The PBX, on receipt of the inbound call,sends the invite to the GS-E (step 614) which replaces the pilot numberwith the original dialed digits using the number that it has previouslystored in association with the pilot number. The GS-E then routes thecall to the PBX for delivery to the desk terminal (step 616). The deskterminal may comprise, for example, a fixed landline telephone device, asoftware client operating on a computing platform, or a mobile terminalcommunicatively interfaced with the PBX. The PBX then routes the call tothe desk terminal (step 618). The desk terminal then returns an inviteacknowledgement (step 620), e.g., a SIP 200 response.

The PBX forwards the acknowledgment to the GS-E (step 622), whichreplies with an acknowledgment (step 624). The PBX then forwards theacknowledgment to the S-CSCF (step 626) which forwards theacknowledgment to the UE over the 3G packet network (step 628), and themedia path is set up (step 630). In this instance, the call comprises apacket switched call leg between the UE and the PBX, the PBX and theenterprise gateway server, and the enterprise gateway server and thedesk terminal.

In the signaling flow 600 b depicted in FIG. 6B, assume the UE now exits3G packetized coverage and moves into a coverage area served only by 2G.Accordingly, the UE now attempts to initiate a handover request to thecarrier's VCC service by originating a call on the 2G network. Afterconversion of the call by the 2G MSC into an IMS call via triggering orother method, an invite is sent to the S-CSCF (step 632). The S-CSCF,based on initial filter criteria, sends the invite to the GS-C forhandling (step 634). If the GS-C allows the handover to occur based oncriteria analyzed in the GS-C (for example, the carrier determines thereis sufficient capacity on the 2G network to continue this call and thesubscription is active or for other based on other carrier policycriteria), then the GS-C forward the request to the GS-E (step 636)hosting the enterprise VCC function. If the GS-E allows the handover tooccur based on criteria analyzed in the GS-E (for example, theenterprise elects to allow the handover to proceed in order to maintainthe call and is willing to accept the 2G call tariffs or for otherenterprise criteria) then the GS-E informs the GS-C to proceed (step638). The GS-C then sends a re-invite for the leg of the call to thedesk phone to the S-CSCF (step 640). The S-CSCF then forwards there-invite to the enterprise PBX (step 642), which forwards the re-inviteto the GS-E (step 644) which responds to the PBX (step 646). The PBXforwards the re-invite to the desk terminal (step 648), and the deskterminal acknowledges the invite (step 650). The PBX then forwards theacknowledgment to the GS-E (step 652) and the GS-E provides anacknowledgment thereto (step 654). The PBX forwards the acknowledgmentto the S-CSCF (step 656) which provides the acknowledgment to the GS-C(step 658) that, in turn, replies with an acknowledgment (step 660). TheS-CSCF then provides an acknowledgement to the 2G MSC (step 662) via aWMG connected to the 2G MSC. The GS-C provides a BYE message to theS-CSCF for terminating the circuit switched call leg (step 664). TheS-CSCF then forwards the BYE message to the UE (step 666) over the 3Gpacket network which may provide an acknowledgment thereto (step 668).The S-CSCF then forwards an acknowledgment to the GS-C (step 670) andthe media path is set up thereby completing the call handover (step672). The call then comprises a 2G, or circuit-switched call leg,between the 2G MSC and a carrier WMG interconnected with the 2G MSC, andpacket-switched call legs between the WMG and the PBX, the PBX and theenterprise gateway server, and the enterprise gateway server and thedesk terminal.

Returning to the case where the UE attempts to initiate a handoverrequest to the carrier's VCC service by sending an invite to the S-CSCF(step 632) and the S-CSCF sends the invite to the GS-C for handling(step 634), if the GS-C instead disallows the handover to occur based oncriteria analyzed in the GS-C (for example, the carrier determines thereis insufficient capacity on the 2G packetized network to handle thiscall or the subscription is inactive), then the GS-C responds with a Byemessage to the S-CSCF (step 682) indicating the handover request hasbeen denied as depicted by the signaling flow 600 c of FIG. 6C. The Byemessage is then sent to the 2G MSC (step 684) via the WMG connected tothe 2G MSC. The handover request is terminated and the UE remains on the3G packet network.

If the GS-C allows the handover to occur, the GS-C then sends therequest to the GS-E for handling (step 636) as depicted by the signalingflow 600 d of FIG. 6D. If instead the GS-E disallows the handover tooccur based on criteria analyzed in the GS-E (for example, theenterprise elects to maintain the call on the 3G network to avoid 2Gtariffs or for other policy reasons), then the GS-E responds with a Byemessage to the GS-C indicating the handover request has been denied(step 680), which is sent to the S-CSCF (step 682) indicating thehandover request has been denied. The Bye message is then sent to the 2GMSC (step 684) via the WMG connected to the 2G MSC. The handover requestis terminated and the UE remains on the 3G packet network.

FIGS. 7A-7D depict exemplary signaling flows for a multi-mode mobilehandover featuring voice call continuity from a packet network to acircuit network implemented in accordance with another embodimentwhereby seamless handover mechanisms are provided for calls establishedon the enterprise side of the network by enterprise VCC capabilities.

In this implementation, the enterprise GS-E acts as the primary contactpoint by the multi-mode device when a handover is to occur, and as suchthe GS-E performs the VCC handover with permission obtained from theGS-C. In the particular example, a call is handed off between anunlicensed WiFi packet voice network and a 2G circuit network whileremaining anchored in the enterprise such that enterprise services,e.g., PBX features, call monitoring, and the like, may be provided tothe call and maintained over the seamless handover.

In the signaling flow 700 a of FIG. 7A, the user of a multi-mode deviceoriginates a packetized voice call over the WiFi network to a desk phonein the enterprise. A call invite is issued by the UE over the WiFipacket network to the GS-E (step 702). The GS-E forwards the invite tothe PBX (step 704) which delivers the call to the desk terminal (step706). The desk terminal then returns an invite acknowledgement (step708), e.g., a SIP 200 response.

The PBX forwards the acknowledgment to the GS-E (step 710), whichreplies to the UE with an acknowledgment (step 712) and the media pathis set up (step 714). In this instance, the call comprises a packetswitched call between the UE and the PBX, the PBX and the enterprisegateway server, and the enterprise gateway server and the desk terminal.

Following therefrom as depicted in the signaling flow 700 b of FIG. 7B,assume the UE moves away from WiFi coverage and into a 2G coverage area.Accordingly, the UE now attempts to initiate a handover request to theenterprise's VCC service by sending a notification over the WiFi networkto the GS-E hosting the enterprise VCC function (step 720).

The handover request by the UE over the WiFi network may be sent to anIP address or to a domain name that is resolved to the enterprise's VCCservice. If the GS-E allows the handover to occur based on criteriaanalyzed in the GS-E (for example, the enterprise elects to allow thehandover in order to maintain the call and accept the 2G tariffs or forother enterprise criteria), then the GS-E forward the request to theGS-C (step 722) hosting the carrier VCC function. If the GS-C allows thehandover to occur based on criteria analyzed in the GS-C (for example,the carrier identifies that the enterprise has subscribed to thisservice, the carrier identifies there is sufficient 2G capacity for thecall, or for other carrier policy criteria) then the GS-C informs theGS-E to proceed (step 724).

The GS-E then sends an invite to the PBX to originate a call to themulti-mode mobile on the 2G network (step 728). The outbound PBX call tothe 2G MSC may traverse the PSTN via a media gateway in the enterpriseconnected to the PBX. On a successful connection to the multi-modedevice on the 2G network, the 2G MSC responds to the PBX via the PSTN(step 730). The PBX sends an acknowledgement to the GS-E (step 732)which then sends a re-invite for the leg of the call to the desk phoneto the PBX (step 734) which in turn sends the re-invite to the deskphone (step 736). The desk phone then provides an acknowledgement to thePBX (step 738) which responds to the GS-E (step 740).

The GS-E informs the UE over the WiFi network to terminate the WiFi legwith a Bye message (step 742) and the media path is set up therebycompleting the call handover (step 744). The call then comprises a 2G,or circuit-switched call leg, between the 2G MSC and a carrier WMGinterconnected with the 2G MSC, and packet-switched call legs betweenthe WMG and the PBX, the PBX and the enterprise gateway server, and theenterprise gateway server and the desk terminal.

Returning to the case where the UE attempts to initiate a handoverrequest to the enterprise's VCC service by sending an invite to the GS-E(step 720) and the GS-E sends the invite to the GS-C for permission(step 722), if the GS-C instead disallows the handover to occur based oncriteria analyzed in the GS-C (for example, the carrier determines thereis insufficient capacity on the 2G network, the enterprise has notsubscribed to this service or other policy reasons), then the GS-Cresponds with a Bye message to the GS-E (step 750) as depicted in thesignaling flow 700 c of FIG. 7C. The Bye message indicates the handoverrequest has been denied, and the handover request does not proceed. TheUE remains on the WiFi packet network.

If instead the GS-E disallows the handover to occur based on criteriaanalyzed in the GS-E (for example, the enterprise elects to maintain thecall on the WiFi network to avoid 2G tariffs or for other enterprisepolicy criteria), then the GS-E ignores the notification as depicted bythe signaling flow 700 d in FIG. 7D. The handover request does notproceed and the UE remains on the WiFi packet network.

FIG. 8 is a flowchart 800 that depicts processing of an enterprise voicecall continuity routine that facilitates handover collaboration betweena carrier network and an enterprise network in accordance with anembodiment. The processing steps of FIG. 8 may be implemented ascomputer-executable instructions tangibly embodied on acomputer-readable medium executable by a processing system, such as theGS-E 176 depicted in the network system 100 of FIG. 1.

The enterprise VCC routine is invoked (step 802), and a request forhandover of an enterprise member UE from a circuit switched network to apacket switched network (or, alternatively, from a packet switchednetwork to a circuit switched network) is received by the GS-E (step804). The GS-E may then evaluate enterprise policies (step 806), e.g.,specified in enterprise policy database 178, to determine whether toallow or disallow the handover request (step 808). If the evaluation ofthe enterprise policies indicates that the handover request is notacceptable, the GS-E may then deny the handover (step 810), and the UEremains on the network with which the UE is currently registered. TheGS-E VCC routine cycle may then end (step 818).

Returning to step 808, in the event that the GS-E determines thehandover request is acceptable based on the evaluated enterprisepolicies, the GS-E may then evaluate if the handover request wasreceived from the GS-C (step 812). If the handover request was receivedfrom the GS-C thereby indicating the GS-C has approved the handoverrequest, the GS-E may then invoke the handover (step 814). For example,the GS-C will receive and allow or disallow the handover request whenthe UE is currently registered in the carrier network. In the event theGS-C allows the handover request, the GS-C will forward the handoverrequest to the GS-E for evaluation of the handover request according tothe enterprise policies. Upon invocation of the handover, the GS-E VCCroutine cycle may then end according to step 818.

Returning again to step 812, in the event that the handover request wasnot received by the GS-E from the GS-C, the GS-E then forwards thehandover request to the GS-C (step 816). For example, if the UE iscurrently registered in the enterprise network when the handover requestis issued by the UE, the handover request will be transmitted to theGS-E for evaluation thereby. If the GS-E approves the handover request,the GS-E then forwards the request to the GS-C for evaluation of therequest according to the carrier policies. After forwarding the handoverrequest to the GS-C, the GS-C VCC routine cycle then ends according tostep 818.

FIG. 9 is a flowchart 900 that depicts processing of a carrier voicecall continuity routine that facilitates handover collaboration betweena carrier network and an enterprise network in accordance with anembodiment. The processing steps of FIG. 9 may be implemented ascomputer-executable instructions tangibly embodied on acomputer-readable medium executable by a processing system, such as theGS-C 192 depicted in the network system 100 of FIG. 1.

The carrier VCC routine is invoked (step 902), and a request forhandover of an enterprise member UE from a circuit switched network to apacket switched network (or, alternatively, from a packet switchednetwork to a circuit switched network) is received by the GS-C (step904). The GS-C may then evaluate carrier policies (step 906), e.g.,specified in carrier policy database 194, to determine whether to allowor disallow the handover request (step 908). If the evaluation of thecarrier policies indicates that the handover request is not acceptable,the GS-C may then deny the handover (step 910), and the UE remains onthe network with which the UE is currently registered. The GS-C VCCroutine cycle may then end (step 918).

Returning to step 908, in the event that the GS-C determines thehandover request is acceptable based on the evaluated carrier policies,the GS-C may then evaluate if the handover request was received from theGS-E (step 912). If the handover request was received from the GS-Ethereby indicating the GS-E has approved the handover request, the GS-Cmay then invoke the handover (step 914). For example, the GS-E willreceive and allow or disallow the handover request prior to receipt ofthe handover request by the GS-C when the UE is currently registered inthe enterprise network. In the event the GS-E allows the handoverrequest, the GS-E will forward the handover request to the GS-C forevaluation of the handover request according to the carrier policies.Upon invocation of the handover, the GS-C VCC routine cycle may then endaccording to step 918.

Returning again to step 912, in the event that the handover request wasnot received by the GS-C from the GS-E, the GS-C then forwards thehandover request to the GS-E (step 916). For example, if the UE iscurrently registered in the carrier network when the handover request isissued by the UE, the handover request will be transmitted to the GS-Cfor evaluation thereby. If the GS-C approves the handover request, theGS-C then forwards the request to the GS-E for evaluation of the requestaccording to the enterprise policies. After forwarding the handoverrequest to the GS-E, the GS-E VCC routine cycle then ends according tostep 918.

The flowcharts of FIGS. 8-9 depict process serialization to facilitatean understanding of disclosed embodiments and are not necessarilyindicative of the serialization of the operations being performed. Invarious embodiments, the processing steps described in FIGS. 8-9 may beperformed in varying order, and one or more depicted steps may beperformed in parallel with other steps. Additionally, execution of someprocessing steps of FIGS. 8-9 may be excluded without departing fromembodiments disclosed herein.

The illustrative block diagrams and flowcharts depict process steps orblocks that may represent modules, segments, or portions of code thatinclude one or more executable instructions for implementing specificlogical functions or steps in the process. Although the particularexamples illustrate specific process steps or procedures, manyalternative implementations are possible and may be made by simpledesign choice. Some process steps may be executed in different orderfrom the specific description herein based on, for example,considerations of function, purpose, conformance to standard, legacystructure, user interface design, and the like.

Aspects of the present invention may be implemented in software,hardware, firmware, or a combination thereof. The various elements ofthe system, either individually or in combination, may be implemented asa computer program product tangibly embodied in a machine-readablestorage device for execution by a processing unit. Various steps ofembodiments of the invention may be performed by a computer processorexecuting a program tangibly embodied on a computer-readable medium toperform functions by operating on input and generating output. Thecomputer-readable medium may be, for example, a memory, a transportablemedium such as a compact disk, a floppy disk, or a diskette, such that acomputer program embodying the aspects of the present invention can beloaded onto a computer. The computer program is not limited to anyparticular embodiment, and may, for example, be implemented in anoperating system, application program, foreground or background process,driver, network stack, or any combination thereof, executing on a singlecomputer processor or multiple computer processors. Additionally,various steps of embodiments of the invention may provide one or moredata structures generated, produced, received, or otherwise implementedon a computer-readable medium, such as a memory.

Although embodiments of the present disclosure have been described indetail, those skilled in the art should understand that they may makevarious changes, substitutions and alterations herein without departingfrom the spirit and scope of the present disclosure.

What is claimed is:
 1. A method, comprising: locating, by a userequipment registered in a first network, a second network, wherein oneof the first network and the second network comprises a circuit switchednetwork and another of the first network and the second networkcomprises a packet switched network; transmitting, by the userequipment, a request for a handover to the second network, the requestbeing received by at least one of an enterprise gateway server of thepacket switched network and a carrier gateway server of the circuitswitched network; and determining, by a voice call continuity service,whether to allow the handover by an enterprise network node and acarrier network node, wherein whether to allow the handover comprises atleast one of dual approval by both the enterprise network node and thecarrier network node and single approval by one of the enterprisenetwork node and the carrier network node which is designated as anoverride authority, wherein the enterprise network node is controlled byan enterprise network and the carrier network node is controlled by acarrier network.
 2. The method of claim 1, wherein the enterprisenetwork node comprises an enterprise gateway server and the carriernetwork node comprises a carrier gateway server, and wherein determiningwhether to allow the handover comprises: receiving, by the enterprisegateway server, the handover request; and evaluating, by the enterprisegateway server, an enterprise policy.
 3. The method of claim 2, furthercomprising determining, by the enterprise gateway server, to disallowthe handover based on the enterprise policy.
 4. The method of claim 2,further comprising: determining, by the enterprise gateway server, toallow the handover based on the enterprise policy; notifying, by theenterprise gateway server, the carrier gateway server of the handoverrequest; and evaluating, by the carrier gateway server, a carrierpolicy.
 5. The method of claim 4, further comprising: disallowing, bythe carrier gateway server, the handover based on the carrier policy;and notifying, by the carrier gateway server, the enterprise gatewayserver that the handover request is denied.
 6. The method of claim 4,further comprising: allowing, by the carrier gateway server, thehandover based on the carrier policy; and completing handover of theuser equipment from the first network to the second network.
 7. Themethod of claim 1, wherein the enterprise network node comprises anenterprise gateway server and the carrier network node comprises acarrier gateway server, and wherein determining whether to allow thehandover comprises: receiving, by the carrier gateway server, thehandover request; evaluating, by the carrier gateway server, a carrierpolicy; and determining, by the carrier gateway server, to disallow thehandover based on the carrier policy.
 8. The method of claim 1, whereinthe enterprise network node comprises an enterprise gateway server andthe carrier network node comprises a carrier gateway server, and whereindetermining whether to allow the handover comprises: receiving, by thecarrier gateway server, the handover request; evaluating, by the carriergateway server, a carrier policy; determining, by the carrier gatewayserver, to allow the handover based on the carrier policy; notifying, bythe carrier gateway server, the enterprise gateway server of thehandover request; and evaluating, by the enterprise gateway server, anenterprise policy to determine whether to allow the handover.
 9. Themethod of claim 8, further comprising: allowing, by the enterprisegateway server, the handover; and completing handover of the userequipment from the first network to the second network.
 10. Anon-transitory computer-readable medium having computer-executableinstructions for execution by a processing system, thecomputer-executable instructions, when executed, cause the processingsystem to: receive a request for a handover of a user equipment from afirst network in which the user equipment is registered to a secondnetwork, wherein one of the first network and the second networkcomprises a circuit switched network and another of the first networkand the second network comprises a packet switched network, the requestbeing received by at least one of an enterprise gateway server of thepacket switched network and a carrier gateway server of the circuitswitched network; and determine, by a voice call continuity service,whether to allow the handover by an enterprise network node and acarrier network node, wherein whether to allow the handover comprises atleast one of dual approval by both the enterprise network node and thecarrier network node and single approval by one of the enterprisenetwork node and the carrier network node which is designated as anoverride authority, wherein the enterprise network node is controlled byan enterprise network and the carrier network node is controlled by acarrier network.
 11. The non-transitory computer-readable medium ofclaim 10, wherein the enterprise network node comprises an enterprisegateway server and the carrier network node comprises a carrier gatewayserver, and wherein the instructions that determine whether to allow thehandover comprise instructions that, when executed, cause the processingsystem to: evaluate, by the enterprise gateway server, an enterprisepolicy; and determine, by the enterprise gateway server, to disallow thehandover based on the enterprise policy.
 12. The non-transitorycomputer-readable storage medium of claim 10, wherein the enterprisenetwork node comprises an enterprise gateway server and the carriernetwork node comprises a carrier gateway server, and wherein theinstructions that determine whether to allow the handover compriseinstructions that, when executed, cause the processing system to:evaluate, by the enterprise gateway server, an enterprise policy;determine, by the enterprise gateway server, to allow the handover basedon the enterprise policy; notify, by the enterprise gateway server, thecarrier gateway server of the handover request; and evaluate, by thecarrier gateway server, a carrier policy.
 13. The non-transitorycomputer-readable storage medium of claim 12, further comprisinginstructions that, when executed, cause the processing system to:disallow, by the carrier gateway server, the handover based on thecarrier policy; and notify, by the carrier gateway server, theenterprise gateway server that the handover request is denied.
 14. Thenon-transitory computer-readable storage medium of claim 12, furthercomprising instructions that, when executed, cause the processing systemto: allow, by the carrier gateway server, the handover based on thecarrier policy; and complete handover of the user equipment from thefirst network to the second network.
 15. The non-transitorycomputer-readable storage medium of claim 10, wherein the enterprisenetwork node comprises an enterprise gateway server and the carriernetwork node comprises a carrier gateway server, and wherein theinstructions that determine whether to allow the handover compriseinstructions that, when executed, cause the processing system to:receive, by the carrier gateway server, the handover request; evaluate,by the carrier gateway server, a carrier policy; and determine, by thecarrier gateway server, to disallow the handover based on the carrierpolicy.
 16. The non-transitory computer-readable storage medium of claim10, wherein the enterprise network node comprises an enterprise gatewayserver and the carrier network node comprises a carrier gateway server,and wherein the instructions that determine whether to allow thehandover comprise instructions that, when executed, cause the processingsystem to: receive, by the carrier gateway server, the handover request;evaluate, by the carrier gateway server, a carrier policy; determine, bythe carrier gateway server, to allow the handover based on the carrierpolicy; notify, by the carrier gateway server, the enterprise gatewayserver of the handover request; and evaluate, by the enterprise gatewayserver, an enterprise policy to determine whether to allow the handover.17. A communication network system, comprising: a carrier network thatincludes a carrier gateway server and a carrier policy database; anenterprise network that includes an enterprise gateway servercommunicatively coupled with the carrier gateway server and anenterprise policy database; and a user equipment associated with theenterprise network, wherein the user equipment is registered in a firstnetwork and transmits a request for handover to a second network,wherein one of the first network and the second network comprises acircuit switched network and another of the first network and the secondnetwork comprises a packet switched network, and wherein the request isreceived by at least one of the enterprise gateway server of the packetswitched network and the carrier gateway server of the circuit switchednetwork wherein the carrier network and the enterprise networkcollaboratively provide a voice call continuity service, wherein whetherto allow the handover comprises at least one of dual approval by boththe enterprise gateway server and the carrier gateway server and singleapproval by one of the enterprise gateway server and the carrier gatewayserver which is designated as an override authority.
 18. The networksystem of claim 17, wherein the first network is controlled by theenterprise network, wherein the enterprise gateway server receives thehandover request and, upon approval of the handover request based on anevaluation of the enterprise policy database by the enterprise gatewayserver, forwards the handover request to the carrier gateway server forevaluation of the handover request.
 19. The network system of claim 17,wherein the first network is controlled by the carrier network, whereinthe carrier gateway server receives the handover request and, uponapproval of the handover request based on an evaluation of the carrierpolicy database by the carrier gateway server, forwards the handoverrequest to the enterprise gateway server for evaluation of the handoverrequest.
 20. A method for providing handover services in disparatepacket switched networks, comprising: receiving a request for a handoverfrom a user equipment from a first packet switched network in which theuser equipment is registered to a second packet switched network, therequest being received by an enterprise gateway server of the secondpacket switched network, wherein the first packet switched network andthe second packet switched network operate in different packet switchedmodes; and determining whether to allow the handover by an enterprisenetwork node and a carrier network node, wherein a requirement to allowthe handover comprises at least one of dual approval by both theenterprise network node and the carrier network node and single approvalby one of the enterprise network node and the carrier network node whichis designated as an override authority, wherein the enterprise networknode is controlled by an enterprise network and the carrier network nodeis controlled by a carrier network.
 21. The method of claim 20, whereinevaluating the request comprises: receiving, by the enterprise networknode, the request; determining, by the enterprise network node, to allowthe handover; and forwarding, by the enterprise network node, therequest to the carrier network node for evaluation of the request. 22.The method of claim 20, wherein evaluating the request comprises:receiving, by the carrier network node, the request; determining, by thecarrier network node, to allow the handover; and forwarding, by thecarrier network node, the request to the enterprise network node forevaluation of the request.